Fiber reinforced composite materials typified by fiber reinforced plastics (FRP), in particular, carbon fiber reinforced plastics (CFRP), have large tensile strength and tensile elastic force and small density, as compared with glass fiber reinforced plastics (GFRP), aramid fiber reinforced plastics (AFRP), or stainless steel (SUS), and have therefore tended to be frequently used as outer panels or the like of aircrafts or vehicles in recent years. In this context, CFRP refers to plastics prepared by hot molding or hot press molding one or two or more layers of prepregs containing carbon fiber impregnated with a matrix resin. A member formed from this CFRP is fixed to a structure using a fastening factor such as a bolt or a rivet. Therefore, cutting work, in particular, cutting work to make many holes for passing a fastening factor in CFRP, is necessary for fixing CFRP to a structure such as an aircraft part.
Some techniques have already been proposed in order to obtain high quality holes by the cutting work of CFRP. Examples of such a technique include a method which involves gradually changing the shape of a tool, for example, the curvature of a cutting face or the point angle of a drill (see, for example, Patent Literature 1).